{1} The Fifth Amendment commands that no
person "shall be compelled in any criminal case to be a witness
against himself."[1]
However, extending current judicial interpretations of the Fourth
and Fifth Amendments too far may allow the government easy access
even to private documents, making one's diary and other documents
accessible and admissible in court against their author.

{2} What the Court has taken away, technology
has given. Modern cryptography can make it virtually impossible
to decipher documents without the cryptographic key,[2] thus making the availability of the contents
of those documents depend on the availability of the key. This
article examines the Fourth and Fifth Amendments' protection against
the compulsory production of the key and the scope of the Fifth
Amendment immunity against compelled production. After analyzing
these questions using prevailing Fourth and Fifth Amendment jurisprudence,
I shall describe the advantages of a privacy-based approach in
practical and constitutional terms.

{3} The Fourth Amendment provides little
protection from the search and seizure of documents. In Warden
v. Hayden,[3] the
Court discarded the rule that the power to search and seize depended
on the assertion of a superior right to the property seized. Before
Warden,officers could search for fruits of a crime,
because a superior right was in the property owners; for contraband,
because no one could legally own contraband; and for instrumentalities,
because their role in the commission of the crime made them forfeitable;
but could not search for mere evidence.[4] Because, for example, diaries are "mere
evidence," the Warden rule potentially could allow
search warrants to seize diaries and other purely private documents.
Although Warden expressly refused to consider "whether
there are items of evidential value whose very nature precludes
them from being the object of a reasonable search and seizure,"[5] many now believe that
all objects can be seized.[6]

{4} The Fifth Amendment's guarantee against
self incrimination also provides little protection for existing
documents. The Court generally interprets the Fifth Amendment
to allow the government to compel the production of these
documents, because the government did not compel anyone to write
the documents.[7]
Thus, the government can compel the production of documents and,
if written, the key encrypting the documents. Although there may
still be some protection for private documents, such protection
is uncertain in its existence and narrow in its scope.[8]

{5} Under the Warden view and Fifth
Amendment jurisprudence, written cryptographic keys cannot be
distinguished from the documents themselves. If the key is found
by a search, it can be used. If one can subpoena the underlying
documents, one can subpoena the key.

{6} In this section, I shall assume the
correctness of Justice O'Connor's belief that there is now no
Fourth or Fifth Amendment obstacle to the compulsory production
of existing documents, whether text, encrypted text, or cryptographic
key.[9] This means that
the basis of protection must be an assertion of Fifth Amendment
privilege against a question asking one to disclose a memorized
cryptographic key.

{7} Because current law may hold that the
underlying, pre-existing documents can be the subject of a search
or subpoena, Fifth Amendment analysis must focus on the disclosure
of the cryptographic key on the assumption that the key is not
written down. The Fifth Amendment is now interpreted to bar only
the production of "testimonial information,"[10] so the protection of the Fifth Amendment
extends only to an incriminating communication that might "itself,
explicitly or implicitly, relate a factual assertion or disclose
information."[11]

{8} A non-cryptographic key is physical
evidence, not testimonial evidence.[12]
Thus, the Court has upheld both a Fourth Amendment seizure[13] and the compulsory
production of such non-testimonial evidence, such as a blood sample[14] or the performance
of sobriety tests that do not involve communication.[15]

{9} A cryptographic key need not have testimonial
content. A key can be any word, phrase, or a series of randomly
chosen digits. However, one can imagine a cryptographic key that
has been given an incriminating, testimonial content by making
it a word or phrase that confesses to a crime. Many seldom-enforced
statutes[16] enable
one to confess to a crime in one's cryptographic key, thereby
triggering potential criminal liability and therefore the protection
of the Fifth Amendment,[17]
without incurring much risk of prosecution or of social obloquy
should the key leak or the Fifth Amendment argument be rejected.
However, many keys will not confess to a crime. So, while this
may be a factor for the prudent in selecting particular cryptographic
keys, it cannot be relied upon to resolve the problems before
the courts.[18]

{10} Because a cryptographic key need
not be testimonial and will ordinarily not be testimonial, it
might be argued that the disclosure of the key could be compelled
without raising Fifth Amendment issues. Why should a cryptographic
key be protected from production if a non-cryptographic key such
as the key to a safe, is not?[19]

{11} The difficulty in distinguishing
the two cases is exacerbated by the ability of circumstances to
cause the same information to be expressed in testimonial and
non-testimonial ways. For example, producing a key to a safe implicitly
asserts that the key I turn over is the key to the safe and implicitly
admits my control over the key. These implicit admissions cannot
be used against the producer of the key. However, the key itself
will not be suppressed. One could easily consider the production
of the key an implicit description of the shape of the key, perhaps
in a standardized form common to locksmiths, in which case I have
made a testimonial assertion about the key and the relation of
the key so described to the safe that the key opened.

{12} Despite the functional identity between
these keys, the Court has already suggested in dictum that there
is a fine line that distinguishes testimonial from non-testimonial
compulsion. In Doe v. United States (Doe II), the Court
recognized that "be[ing] compelled to reveal the combination
to his wall safe" would be testimonial compulsion, but suggested
that the key to a strongbox containing incriminating documents
would not be.[20]

{13} The Court's conclusion in Doe
II appears to be consistent with its other cases. The argument
that the Fifth Amendment allows the compulsory disclosure of a
combination confuses the requirement that the statement be testimonial
with the argument that the Fifth Amendment requires that the thing
about which the statement is made be testimonial. Although the
key has no testimonial content, a statement concerning the key
is testimonial. The same would be true of a murder weapon. The
murder weapon itself is not testimonial, but the suspect's statement
about the location of the murder weapon would be testimonial.
So, too, would the disclosure of the key associated with particular
encrypted documents be testimonial. Thus, if a custom-designed
chip included the key in hardware or firmware, the production
of the chip could be compelled, just as physical evidence or a
pre-existing document could be compelled.

{14} The difficulties with the boundary
line the Court has drawn between testimonial and non-testimonial
information are not unique to cryptographic keys. For example,
although evidence about someone's physical state is not considered
testimonial information, the use of heart rate and skin resistance
as part of a polygraph test might well be considered testimonial.
"[E]ven a subject unwilling throughout would presumably provide
revealing lie-detector responses if bombarded by words meaningful
in the context of the crime being investigated-'hammer!' 'club!'
'wrench!' 'pipe!'"[21]
The Supreme Court suggested in Schmerber that the results
of such a test would be inadmissible:

Some tests seemingly directed to obtain "physical evidence,"
for example, lie detector tests measuring changes in body function
during interrogation, may actually be directed to eliciting responses
which are essentially testimonial. To compel a person to submit
to testing in which an effort will be made to determine his guilt
or innocence on the basis of physiological responses, whether
willed or not, is to evoke the spirit and history of the Fifth
Amendment. Such situations call to mind the principle that the
protection of the privilege "is as broad as the mischief
against which it seeks to guard."[22]

{15} Conversely, testimonial information
sought not for the truth of the information, but to reveal an
underlying physical state, is inadmissible under the Fifth Amendment.
Pennsylvania v. Muniz[23]
involved a videotape of someone who had been arrested for drunk
driving. At one point, the defendant's interrogator asked him
when his sixth birthday was.[24]
The questioner was not interested in the actual date of the birthday,
but in "the incriminating inference of impaired mental faculties
. . . from a testimonial aspect of that response."[25] Although the inquisitor was not interested
in obtaining a truthful answer, the Supreme Court held that the
question implicated the Fifth Amendment.[26]

{16} These boundary lines cannot easily
be extended to make disclosure of cryptographic keys non-testimonial.
Ambiguities could be used to extend the Fifth Amendment to the
production of implicitly testimonial conduct, such as the production
of safe keys. However, to hold that an expressly assertive statement
was non-testimonial would effectively eliminate the Fifth Amendment's
protection against self-incrimination. A cryptographic key can
be likened to testimonial statements. Consequently, it seems safe
to conclude that the compulsory production of a cryptographic
key implicates the Fifth Amendment.

{17} If, as the above argument suggests,
the identification of the key is testimonial, the critical issue
will be the extent of the immunity necessary to satisfy the Fifth
Amendment's proscription of self-incrimination.[27] The federal government has suggested that
it will seek to grant immunity as a tool for discovering encrypted
documents.[28] Does
immunity extend only to the key or does it also cover the decrypted
document produced by applying the key to the encrypted text?

{18} The Supreme Court has distinguished
between incriminating documents, which may not be protected by
the privilege, and the incriminating aspects of producing the
documents, from which one may claim Fifth Amendment immunity even
if the documents themselves are uncovered.[29] Thus, in United States v. Doe (Doe I),
the Court held that the production of individual tax records in
the individual's possession might have testimonial and self-incriminating
aspects such that their production could only be required through
a grant of use immunity.[30]
Although it has been suggested that derivative immunity for encrypted
documents would follow as a matter of course from the production
of the key,[31] this
line of cases suggests otherwise.

{19} The leading authority here is Justice
White's opinion for the Court in Fisher, which discusses
the testimonial aspects of production as though the courts could
compel production so long as the amount of self-incrimination
is not excessive.[32]
The same sort of reasoning appears in other cases, even when those
cases have resolved this analysis in favor of the individual.
For example, in Doe I, the Court upheld a refusal to comply
with a subpoena absent a grant of immunity because the incriminating
effects of production were not "trivial."[33]Doe I distinguished Fisher
as a case where "the act of production would have only minimal
testimonial value and would not operate to incriminate the taxpayer."[34]

{20} Fisher did not address the
issue of derivative use immunity where the government would not
have found the documents without a subpoena. This is because Fisher
involved a situation in which the government could certainly get
the documents without the aid of the subpoena. "The existence
and location of the papers are a foregone conclusion and the taxpayer
adds little or nothing to the sum total of the Government's information
by conceding that he in fact has the papers."[35] Because the government did not need the
subpoena to get the papers, it had sufficiently shown an independent
route to the papers to make them admissible without violation
of the Fifth Amendment.

{21} It is not certain that the Court
still follows this narrow view of Fisher. In Braswell
v. United States, a case following Fisher, the dissent
argued without opposition from the majority that documents produced
pursuant to a claim of privilege could nonetheless be used against
the producer, so long as the testimonial effect of the production
itself was shielded.[36]

{22} On the other hand, the Court has
not held that documents compulsorily produced can automatically
be used against the producer. Fisher does discuss the actual
effect of production; the facts of the case, in which the papers
were initially in the hands of the accountant, support the Court's
conclusion that the production of the papers did not increase
the government's information. Nothing in Fisher, then,
can be interpreted to mean that the Fifth Amendment allows the
derivative use of documents which the government could not independently
find and authenticate.[37]Doe I, subsequent to Fisher, held that the documents
in question need not have been produced,[38] and in the absence of a request for use
immunity, the Court did not deal with the issue of derivative
use immunity.[39]Doe
II, also subsequent to Fisher, involved the compulsory
signing of a directive to foreign banks without admitting any
information.[40] Because
the Court held that this did not implicate the Fifth Amendment,
that case also did not involve any issue of derivative use immunity.
In Braswell the underlying documents were corporate records
and therefore not privileged,[41]
so derivative use immunity could not apply.

{23} If the broad reading of Fisher
is correct, the presumable basis for Fisher's apparent
conclusion is that the documents themselves do not implicate the
Fifth Amendment because they were not produced under compulsion.
This, of course, makes perfect sense with regard to the documents
considered as original objects of discovery under a search and
seizure permitted by the Fourth Amendment.

{24} However, it neglects the Court's
usual requirement that immunity extend to the derivative use of
any compelled information. The leading case, Kastigar v. United
States, establishes the general rule that the grant of immunity
must include "derivative use immunity": immunity from
"any use, direct or indirect, of the compelled testimony
and any information derived therefrom . . . ."[42]Kastigar "prohibits the prosecutorial
authorities from using the compelled testimony in any respect."[43] The burden is on the
prosecution, which has "the affirmative duty to prove that
the evidence it proposes to use is derived from a legitimate source
wholly independent of the compelled testimony."[44] Thus, use immunity expressly prohibits using
testimony "as an 'investigatory lead'" or using "any
evidence obtained by focusing investigation on a witness as a
result of his compelled disclosures."[45]

{25} In the absence of derivative use
immunity, the Fifth Amendment protection against self-incrimination
places an individual compelled to produce evidence in a better
position than receiving immunity. Kastigar relied on the
Court's prior decision on state-compelled testimony, holding that
"immunity from use and derivative use 'leaves the witness
and the Federal Government in substantially the same position
as if the witness had claimed his privilege' in the absence of
a grant of immunity."[46]
If the information would not have been discovered without the
grant of immunity, the witness is placed in a worse position because
of the grant of immunity.[47]

{26} In its cases involving the production
of documents, the Court seems to have confused the issue of whether
the documents are necessarily privileged with the question of
whether they are the product of compelled testimonial conduct.
The Court was arguably correct in its conclusion that they are
not privileged because their writing was not compelled. Thus,
one can conclude that if the documents had been seized as a result
of a legitimate search, they would be admissible. However, the
Court ignored the question of whether they were the product of
compelled information. If the prosecution immunizes a defendant
and asks her where the murder weapon is, and the prosecution uses
that information to obtain the weapon, it will be barred from
using the weapon to trace the defendant to the crime unless it
can show an independent path. Indeed, the Court has recently re-affirmed
its statement in Curcio v. United States[48] that the custodian of documents cannot be
compelled to answer questions about the documents' location without
a grant of use immunity.[49]
Under the Court's precedents, such a grant implies that documents
discovered or produced as a result of the answers to such questions
would be suppressed as the product of the compelled testimony.[50] A subpoena to produce
the documents implicitly requires the same information as would
result from the answering of questions about the documents' location,
so a distinction in the scope of derivative immunity in the two
cases seems unjustified. Indeed, the Court's earlier cases expressly
equate documents discovered by compulsory production and documents
discovered by compulsory testimony, which then leads to the documents:

In practice the result is the same to one accused of a crime,
whether he be obliged to supply evidence against himself or whether
such evidence be obtained by an illegal search of his premises
and seizure of his private papers. In either case he is the unwilling
source of the evidence, and the Fifth Amendment forbids that
he shall be compelled to be a witness against himself in a criminal
case.[51]

{27} In Fisher and progeny, the
defendant failed sufficiently to exclude the possibility of independent
discovery. So far as holdings go, as opposed to statements, there
is nothing in the Supreme Court's decisions from Fisher
to the present that excludes the possibility of its rejecting
its ill-conceived and inconsistent assumptions on derivative use
immunity in the case of documents. Even the statements are rare,
being confined to a dissenter's assertion in Braswell.[52]

{28} Thus, it is still open for the Court
to conclude that its conventional doctrines of use immunity apply
to documentary production. In the context of cryptographic keys,
that would ensure that the compulsory production of the key provided
derivative use immunity for the contents of the documents decrypted
with the key.

{29} Even if the Court concludes that
derivative use immunity does not generally apply to documents
discovered with the aid of compelled testimony, there are special
reasons for extending Fifth Amendment immunity to documents decrypted
with the aid of the compelled production of a cryptographic key.

{30} One unique property of a cryptographic
key is that it creates communicative content. Producing an ordinary
document or making available a key to a safe does not alter the
communicative content of the documents produced or made available.
In contrast, producing a cryptographic key gives the document
a testimonial content by decrypting the document and returning
it into plaintext. Thus, the compulsory production of the key
is the compulsory creation of testimonial content. Without the
key, the documents would not be useful as testimony.[53]

{31} Several Supreme Court opinions suggest
that the creation of documentary evidence in this fashion triggers
Fifth Amendment protection. The Court has held that the protection
of the Fifth Amendment extends to any incriminating communication
that might "itself, explicitly or implicitly, relate a factual
assertion or disclose information."[54] The production of a cryptographic key indirectly
relates the material contained in the document decrypted with
the cryptographic key and should therefore lead to immunity under
the Fifth Amendment for the document produced with the key.

{32} Elsewhere, the Court has stated that
it "do[es] not view the exhibition of physical characteristics
to be equivalent to the creation of documentary evidence."[55] The Court's concern
with "the creation of documentary evidence" also suggests
that the compulsory production of the cryptographic key, which
makes possible the creation of the documentary evidence to be
used in court, provides immunity as to the documents that could
be created only with the key.

{33}Finally, Fisher and Doe
I stated that the production sought in those cases "does
not . . . ordinarily compel the taxpayer to restate, repeat, or
affirm the truth of the contents of the documents sought."[56] Thus, although a person
may be compelled to produce a document, compulsory production
cannot require her to repeat, affirm, or explain the contents
of the document. However, the compulsory production of the key
does force the repetition of the document in a new and courtroom-usable
form. Under these precedents, then, the compulsory production
of a key should give rise to immunity from culpability derived
from the document produced with the key.

{34} Even if it were argued that it is
the document and the key that jointly create the testimonial content,
that is sufficient, because self-incrimination protection extends
to all the "links [that] frequently compose that chain of
testimony which is necessary to convict any individual of a crime."[57] Thus, an ordinarily
non-privileged item, such as the identity of the client or fee
information, is privileged if the disclosure of the item would
reveal the substance of an attorney-client communication.[58] Because the key is a necessary link in the
chain, it gives rise to immunity from documents with it.

{35} A second unique property of a cryptographic
key is that it can operate as a digital signature, necessarily
authenticating a document.[59]
Indeed, if the person providing the information has never shared
that information with anyone else, a cryptographic key provides
a more effective way of authenticating than locks, because it
is easier to pick locks than to decrypt without a key.[60]

{36} The Fifth Amendment precludes the
compulsory authentication of documents. "[T]he Fifth Amendment
may protect an individual from complying with a subpoena for the
production of his personal records in his possession because the
very act of production may constitute a compulsory authentication
of incriminating information."[61]
"'[T]he constitutional privilege against self incrimination
. . . is designed to prevent the use of legal process to force
from the lips of the accused individual the evidence necessary
to convict him or to force him to produce and authenticate any
personal documents or effects that might incriminate him.'"[62]

{37} The Court noted that where the compulsory
production of documents may authenticate them, "reliev[ing]
the government of the need for authentication," the Fifth
Amendment precludes their production.[63] Although Fisher suggested that no
grant of immunity is necessary where the "possession [of
the documents, their] existence, and authentication were a 'foregone
conclusion,'"[64]
these issues will seldom be indisputable with respect to cryptographic
keys. One difference between "a pre-existing document and
a pre-existing object" is that a prosecutor "can usually
authenticate [a document, such as a diary,] as the defendant's
either by content or handwriting analysis."[65] Authentication in this way will be impossible
without the key. The impossibility of such authentication suggests
that the factual premise of Fisher cannot apply in the
case of computer-encrypted documents, so that compulsory production
of a cryptographic key requires granting use immunity for the
documents decrypted with the key.

{38} Close analysis of cases interpreting
the Fifth Amendment suggests that the amendment does provide protection
against the compulsory production of cryptographic keys. This
protection can result from a reconciliation of the Court's inconsistency
between the compulsory production of documentary evidence and
its more general treatment of the doctrine of derivative use immunity.
Even in the absence of such a reconciliation, the Court's precedents
suggest that it can be expected to hold that the documents produced
from a cryptographic key cannot be used against the producer of
the key, because a cryptographic key authenticates and confers
testimonial content on documents that are otherwise unauthenticated
and meaningless.

{39} This result is quite narrow: only
those who claim to be criminally incriminated by the key or the
decrypted document can claim the protection of the Fifth Amendment.
Although I have suggested a way in which overbroad criminal statutes
can be turned to the advantage of innocent citizens,[66] this result seems unsatisfactory. Why should
criminals have a right to privacy in their documents when non-criminals
do not? The obvious answer is that the Fifth Amendment protects
against self-incrimination, not against invasions of privacy.
However, early American cases provided much broader protection
for privacy. The next section justifies a revival of these early
authorities.

{40} Although early cases provided immunity
from search and seizure and the compulsory production of most
private documents, it is unclear whether any of this early protection
for private documents survives. Justice O'Connor's concurrence
in the Doe II opinion expressed her belief that the Court's opinion
eliminated the possibility of protection for documents. It has
been suggested that her opinion for the court in Baltimore
City Department of Social Services v. Bouknight[67] establishes her Doe II concurrence
as the holding of the Court.[68]

{41} On the other hand, Bouknight involved
an attempt to conceal a child, which is quite a different case
from documents.[69]
The absence of protection for corporate documents results from
the state's power of visitation over corporations, which meant
that their records were not private.[70] The same argument would apply with even
greater force with a child, which could not be said to be the
private property or records of a parent. Moreover, even after
the Court's decision in Baltimore v. Bouknight, the Court
continues to say that the privilege reflects "our respect
for the inviolability of the human personality and of the right
of each individual 'to a private enclave where he may live a private
life.'"[71] This
idea of a private life is difficult to reconcile with a privilege
that applies solely to self-incriminating and testimonial conduct
before a judicial tribunal.

{42} This part of the paper suggests the
outlines of an alternative approach to the problem of confidential
documents and justifies that approach in terms of the Constitution
and its traditional interpretation. Even if the United States
Supreme Court refuses to entertain such an approach, state courts
may be persuaded that such an approach is both more consistent
with the intent of the adopters of the Constitution and contemporary
considerations of policy.

{43} In Boyd v. United States,[72] the Supreme Court
held that "a search and seizure [was] equivalent [to] a compulsory
production of a man's private papers" and that the search
was "an 'unreasonable search and seizure' within the meaning
of the Fourth Amendment."[73]
Under Boyd, the government could not search for private
documents and could not compel their production.

{44} The Boyd decision was based
on a careful review of the intent at the time of the framing and
the practices of the colonial governments to which the framers
objected.[74] Historically,
searches could only be based on the superior property rights of
the government or some other person in the things for which the
search was made.[75]
Thus, one could search for and seize "stolen or forfeited
goods"[76] and
contraband, such as "counterfeit coin, lottery, tickets,
implements of gambling, & c."[77] "Forfeited goods" included the
instrumentalities of the crime, which were forfeited because of
their use in the crime[78]
and included papers that were fruits, contraband, or instrumentalities.[79] Because mere evidence
could not be searched for at the time of the framing, and the
framers intended to adopt these common-law restrictions,[80] these standards defined what the framers
would have understood as a "reasonable" search under
the Fourth Amendment.[81]

{45} Boyd likewise cited the work
of the first congress and contemporary rules of equity in interpreting
the scope of the Fifth Amendment's right against self-incrimination.[82] The Boyd opinion
noted that even the "obnoxious writs of assistance"
did not allow searches for private papers.[83] As the Boyd Court further observed,
the same history showed an absence of power to use process to
seize private papers,[84]
and the first Congress expressly adopted chancery practice, which
forbade the compulsory production of documents.[85] Congress did not enact a statute that could
possibly be construed to allow the seizure of private papers,
whether for use in evidence or in forfeiture, until 1863.[86] The Boyd Court concluded from this
review of practices of the framing that the compulsory production
of private papers or a search for them violated the Fifth Amendment
as well as the Fourth Amendment.[87]

{46} Boyd's antiquity suggests
that it is consistent with the framers' intent. Indeed, both Boyd
and the subsequent Gouled decision expressly placed their
analysis of the Fourth and Fifth Amendments on a historical basis.[88] Subsequent decisions,
although criticizing these cases, have not attacked their historical
basis.[89]

{47} One possible difficulty with Boyd's
argument is that the search and review of papers are themselves
the invasion of privacy. That papers that are mere evidence are
not then carried away does not eliminate the harm from the search.
As Learned Hand wrote, "If the search is permitted at all,
perhaps it does not make so much difference what is taken away,
since the officers will ordinarily not be interested in what does
not incriminate, and there can be no sound policy in protecting
what does."[90]
However, as Hand continued, "Nevertheless, limitations upon
the fruit to be gathered tend to limit the quest itself."[91] In addition, the need
for probable cause for a search, coupled with restrictions on
what the government may seize, could limit the occurrences of
searches of private papers.

{48} Although Boyd's property-oriented
approach to the Fourth and Fifth Amendments provides more support
for privacy than the contemporary privacy-based approach of Katz,[92] it would be wrong
to conclude that the Boyd rule would allow unrestricted
criminality. Under the Boyd line of cases, there could
be no Fifth Amendment rights for corporate papers because of the
state's visitatorial powers.[93]
Under the post-Boyd extension of corporate treatment to
non-corporate collective entities, organizations such as partnerships,
unions, and bankrupt businesses would have no Fifth Amendment
protection.[94] If this
doctrine covers associations in fact,[95] the scope of communications entitled to
Fifth Amendment protection would present few obstacles to law
enforcement.

{49} Similarly, Boyd's principles
allowed the Fourth Amendment seizure of papers sent to another
in pursuit of criminality as the instrumentalities of criminal
acts.[96] As Justice
Marshall observed in dissent, "I see no bar in the Fourth
or Fifth Amendment to the seizure of a letter from one conspirator
to another directing the recipient to take steps that further
the conspiracy.[97]

{50} Boyd's definition of Fourth
and Fifth Amendment rights would also allow the granting of use
immunity to the recipient of a communication to compel the contents
of that communication to be used against the sender, or vice versa.
An individual may not invoke the Fifth Amendment to protect against
incrimination by a third party.[98]
Thus, under the Fifth Amendment, encrypted material that one sends
to another can be discovered by the government by giving the recipient
use immunity for the production of the key, because the Constitution
"does not proscribe incriminating statements elicited from
another."[99]

{51} If the Court continues to reject
Boyd, it will have to reject more than the Boyd
case. The doctrine that there was substantive protection of documents
under the Fourth Amendment and Fifth Amendment, and that an invalid
search or seizure under the Fourth Amendment precluded the use
of the documents was shared in many opinions, some unanimous and
some by the Court's most eminent members. In United States
v. Saline Bank, Chief Justice Marshall, speaking for the Court,
rejected a request for the production of bank documents.[100] "The rule clearly is, that a party
is not bound to make any discovery which would expose him to penalties,
and this case falls within it."[101]Hale v. Henkel affirmed Boyd's
holding that "an order for the production of books and papers
may constitute an unreasonable search and seizure within the Fourth
Amendment."[102]
In Gouled v. United States,[103]
Justice Clarke, speaking for a unanimous court, held when a government
agent seized documents in violation of the Fourth Amendment, their
introduction into court violated the Fifth Amendent.[104] The Court's Silverthorne Lumber opinion
by Justice Holmes and Justice Brandeis' famous Olmstead
dissent are in accord.[105]
Many other cases concur.[106]

{52} Boyd's statement has been
approved as recently as 1973, when United States v. Dionisio[107] stated that
the grand jury "cannot require the production by a person
of private books and records that would incriminate him."[108] In 1976, even after
the Fisher decision, the Court wrote in Andresen v.
Maryland, "'[T]he constitutional privilege against self
incrimination . . . is designed to prevent the use of legal process
to force from the lips of the accused individual the evidence
necessary to convict him or to force him to produce and authenticate
any personal documents or effects that might incriminate him.'"[109]Andresen,
by stating that the government's ability to use information depends
on whether it had been produced by subpoena or search, suggests
that the government was unable to use subpoenaed documents against
their producer.[110]
This result would not have followed from a legitimate search under
the Fourth Amendment.[111]

{53} The erosion of constitutional protection
for private documents proceeded in three ways. First, Warden
v. Hayden abolished the "mere evidence" rule.[112] Although Warden,[113]Fisher,[114] and other cases
have held out the possibility of protection for diaries, the general
rule is that merely evidentiary documents can now be seized without
restriction.[115]

{54} Second, cases have narrowed the scope
of evidence that was considered compelled, so that the compelled
production of documents was not considered the compulsion of the
incriminating evidence in the documents themselves. In Johnson
v. United States, Justice Holmes wrote for the Court, "A
party is privileged from producing the evidence, but not from
its production."[116]
That phrase led to the idea, in subsequent cases, that compelled
production of incriminating information could make the information
usable against the person producing it, if that person were screened
from the testimonial aspects of production.[117] This interpretation is inapplicable to
the facts of Johnson, which did not involve an attempt
to make a party produce evidence by granting that party limited
immunity.[118]

{55} Third, the Court further limited
the Fifth Amendment's protection to extend only to testimonial
evidence. The origin of this line of authority was cases such
as Holmes' opinion in Holt v. United States, which held
that an accused could be compelled to wear a blouse like that
worn by the perpetrator.[119]Holt, however, did not distinguish between the act of producing
information and the testimonial contents of what was compulsorily
produced. Rather, it held that the Fifth Amendment's prohibition
only extended to "physical or moral compulsion to extort
communications from him, not an exclusion of his body as
evidence when it may be material."[120] Wearing the blouse was a physical act
and not a commnuication. However, the threat of contempt certainly
coerces documentary evidence, which is a communication. Thus,
Holt is entirely consistent with Holmes' opinion for the
Court in Silverthorne Lumber, which barred a subpoena for
documents.[121]Holt
is also entirely consistent with opinions that Holmes joined
such as Hale, affirming Boyd's holding that "an
order for the production of books and papers may constitute an
unreasonable search and seizure within the Fourth Amendment,"[122] and Gouled,
holding that when a government agent seized documents in violation
of the Fourth Amendment, their introduction into court violated
the Fifth Amendment.[123]

{56} However, in Fisher v. United States,
the Court stated that the compulsory production of business documents
did not compel testimonial self-incrimination, so it was not prohibited
by the Fifth Amendment.[124]
The Court reasoned that the author of the statements written in
the documents was not compelled to be a witness against himself,
because the author had voluntarily written the statements. The
Court did hold that any inferences drawn from the act of production
itself could be barred.[125]
"The elements of compulsion are clearly present, but the
more difficult issues are whether the tacit averments of the taxpayer
are both 'testimonial' and 'incriminating' for purposes of applying
the Fifth Amendment. These questions perhaps do not lend themselves
to categorical answers; their resolution may instead depend on
the facts and circumstances of particular cases or classes thereof."[126] In that case, the
Court concluded that because the papers had been prepared by the
accountant and were in the hands of the accountant, their production
did not "involve testimonial self-incrimination."[127]

{57} The expansion of other privileges
protecting against intrusion into personal thoughts, including
work-product immunity, attorney-client and spousal privileges,
and self-evaluative privileges, shows that there is no compelling
policy reason for rejecting Boyd.

{58) Work-product immunity had its origin
as a special case of mental privacy, not as a special privilege
for attorneys. As the Court wrote in Hickman v. Taylor,
which invented work-product protection, "[e]xamination into
a person's files and records, including those resulting
from the professional activities of an attorney, must be judged
with care. It is not without reason that various safeguards
have been established to preclude unwarranted excursions into
the privacy of a man's work."[128] If the doctrine of mental privacy is to
be rejected, then the foundation of Hickman and work-product
protection is undermined.

{59} Commonly accepted testimonial privileges
create at least as much social harm as and have fewer benefits
than Boyd's protection for private documents.[129] If I write down my daily activities in
a letter to an attorney or spouse, keeping a copy for myself,
the material is privileged in the hands of the author, the attorney,
and the spouse.[130]
Both the marital privilege and the Boyd privilege for private
documents create a zone of autonomy. "From the perspective
of the individual in Western industrial societies, the marital
relationship is likely to be seen as an extension of one's personal
autonomy . . . . It is in this sense that courts often glimpse
the relationship between the privilege against self-incrimination
and the marital witness privilege."[131]

{60} A diary privilege is even more justified
than an attorney-client privilege. Because of the need for legal
advice, the attorney-client relationship is less likely to be
deterred by a loss of privilege than diary keeping. Moreover,
the attorney-client privilege can be used to evade the law[132] or to convey information
through a corporation without creating a discoverable paper trail,[133] which weakens the
claim for the privilege.

{61} Courts and legislatures have also
been creating new privileges. The courts have judicially expanded
government privileges, even though the legislature can protect
the government. "[G]overnment privileges continue to metastasize."[134] Many jurisdictions
have also protected corporate efforts at self-evaluation under
the rubric of "self-evaluative privileges." These include
general self-evaluative privileges for hospital peer review committees[135] and environmental
audits,[136] and other
authorities have suggested expanding the privilege in other areas.[137]

{62} Thus, contemporary law generally
provides a high degree of privilege for attorneys and those who
consult with them, a fair degree of privilege for governments
and corporations evaluating themselves, and no privilege at all
for those who merely want to write down their ideas. Because the
equivalent of the Boyd privilege is available to those
who have spouses or attorneys and the sophistication to use them
in this way, only the shy, the naive, or the single and impoverished
need give up their right of privacy.

{63} In addition to Boyd's consistency
with the framers' intent and with other privileges created by
a privacy-based approach, its protection of property interests
may protect privacy more effectively than tests directly based
on privacy.

{64} Warden v. Hayden,[138] in which the Supreme Court discerned a
"shift in emphasis from property to privacy"[139] in Fourth Amendment rights, significantly
eroded protection against governmental searches and seizures.
In Warden v. Hayden, the Court upheld the seizure of mere
evidence, although such a seizure would not have been allowed
under property-based interpretations of the Fourth Amendment.
In Katz v. United States,[140]
the Supreme Court followed the Warden v. Hayden decision
and so resolved the "search" of a telephone conversation
by saying that the search invaded privacy, rather than reaching
the same result through property law concepts.[141]

{65} This reconstruction of Fourth Amendment
law to limit the influence of property law concepts was unnecessary.
Justices concurring in the result in Warden v. Hayden said
so in their opinions.[142]
Moreover, Warden v. Hayden based the shift to privacy on
the argument that common law concepts of property could not explain
prior decisions like Silverthorne Lumber, which had returned
copies of documents illegally seized.[143] However, even before Warden, the
Supreme Court protected against the unauthorized copying of material,
similar to that involved in the Silverthorne Lumber.[144] Since Warden,
the expansion of protection of non-physical property has continued.[145] In Katz,
the Court protected against electronic eavesdropping; it could
have held that a user's payment for a phone call gives him a property
interest in the call.[146]

{66} In addition to being unnecessary,
the shift in emphasis in Fourth Amendment analysis from property
law to privacy undermined the privacy interests that Justice Brennan,
the author of Warden v. Hayden, seemed to wish to promote.
The undermining arose from the difficulty in defining limits on
privacy. No one wanted to protect every expectation of
privacy-as the Court pointed out, this would provide constitutional
protection for the burglar justifiably thinking that his presence
in a house would go undiscovered.[147]

{67} To delimit the Fourth Amendment's
protection of privacy, the Court in Rakas v. Illinois began
to confine rights of privacy to those whose expectations of privacy
society considered "reasonable." Under Rakas and
more recent cases following it, "[a] subjective expectation
of privacy is legitimate if it is 'one that society is prepared
to recognize as "reasonable.'"[148]

{68} However, this made the privacy test
circular. How are we to determine that the expectation is "one
that society is prepared to recognize as 'reasonable'"?[149] As the Rakas
Court recognized, "[I]t would, of course, be tautological
to fall back on the notion that those expectations of privacy
which are legitimate depend primarily on cases deciding exclusionary-rule
issues in criminal cases."[150]
To avoid this problem, the Court concluded, "Legitimation
of expectations of privacy by law must have a source outside of
the Fourth Amendment, either by reference to concepts of real
or personal property law or to understandings that are recognized
and permitted by society."[151]

{69} Despite this recognition in the Rakas
opinion of the need to avoid tautology, the Court has generally
ignored or rejected non-criminal-law sources of an expectation
of privacy. The language from the opinion has been used only in
United States v. Jacobsen, and even in that case, the Court
upheld the search.[152]
In Jacobsen, the Court wrote that "the governmental
conduct could reveal nothing about noncontraband items,"
so that the search was justified.[153]
By basing the permissibility of the search on its criminal law
consequences, the Court made it more likely that privacy rights
would arise only in criminal cases. The Court's restriction of
civil claims based on improper searches also reduces the likelihood
that a privacy claim would be heard in a non-criminal context.[154]

{70} More recently, the Court has rejected
the idea that "concepts of privacy under the laws of each
State are to determine the reach of the Fourth Amendment."[155] Thus, even state
law recognition of a right to privacy will not make those expectations
of privacy reasonable for purposes of the Fourth Amendment.[156] The Supreme Court
and state courts frequently differ on what constitutes a reasonable
expectation of privacy.[157]

{71} By defining rights of privacy almost
exclusively with reference to criminal cases, the Supreme Court
has insured that privacy will almost always be pitted against
the interest in convicting a criminal. Tying criminal rights to
property rights created a general interest in protecting criminals
because of the general interest in protecting property rights.
Tying criminal rights to property rights also allowed for the
expansion of rights against the government as new forms of property
arose. Tying criminal rights to a circular test based on "reasonable
expectations" that would only be applied in criminal cases
served neither of these purposes. Instead, this circularity allowed
the Fourth Amendment to be adjusted to the advantage of those
in the legal system best able to protect themselves. The very
uncertainty of the meaning of the word "privacy" promoted
this process.[158]
As a result, in several instances a common law expectation of
privacy exists because a business interest is involved, but the
corresponding interest in privacy under the Fourth Amendment is
held to be unreasonable.[159]

{72} Cryptography may provide a technical
fix for Supreme Court decisions allowing the invasion of one's
private papers. However, the effectiveness of that fix will depend
on whether the Court holds that use immunity from the compulsory
production of a cryptographic key extends to the incriminating
documents decrypted with the key. Logic suggests that the Court
should so hold.

{73} However, the Court's inconsistencies
in this area suggest the limits of logic. The Court has consistently
reconstructed Fourth and Fifth Amendment precedents to move away
from historical practice. This reconstruction is in part responsible
for the Court's inconsistencies.

{74} A more sound approach would be to
adhere to the usual practice of viewing the Fourth and Fifth Amendments
as adopting the practices of the framers at the time of the framing.
This would revive broad protection for merely evidentiary materials.
Moreover, it would allow constitutional protections to evolve
along with social needs, as reflected in society's changing definition
of property.

[1] U.S. CONST.
amend. V. The Fifth Amendment's privilege against self incrimination
was applied to the states through the Fourteenth Amendment in
Malloy v. Hogan, 378 U.S. 1 (1964). This protection means that
no government within the federal system can compel testimony that
would incriminate the witness in proceedings brought before any
other government's courts. Murphy v. Waterfront Comm'n, 378 U.S.
52, 77-78 (1964).

[2] Programs using
encryption keys can now make information highly resistant to decrypting
even if the algorithm for encrypting the information is known.
A. Michael Froomkin, The Metaphor is the Key: Cryptography,
the Clipper Chip, and the Constitution, 143 U. PA.
L. REV. 709,
886
& nn. 767,
768
(1995). For purposes of this paper, the term "cryptographic
key" will refer to that without which the government may
not gain access to the underlying plaintext. In a public key cryptosystem,
this would be the user's private key (and corresponding passphrase);
in a private key cryptosystem, this would be the private key.
It is conceivable that in other cryptosystems, the "key"
could very well be a word or even a phrase.

[9] The original message
is called the "plaintext." A key is used by a cipher
to transmute the plaintext into a ciphertext. Froomkin, supranote 2, at 713-14.

[10]E.g.,
Doe v. United States, 487 U.S. 201 (1988) (Doe II) (stating that
a directive to disclose bank records was not testimonial).

[12]Id. at
210 n.9 (contrasting "be[ing] forced to surrender a key to
a strongbox containing incriminating documents" with "be[ing]
compelled to reveal the combination to [petitioner's] wall safe").
Supreme Court Justices have expressed even further doubt as to
the meaning of "testimonial." California v. Byers, 402
U.S. 424, 462 (1971) (Black, J., dissenting).

[13] Warden v. Hayden,
387 U.S. 294, 302-03 (1967) ("The items of clothing involved
in this case are not 'testimonial' . . . in nature, and their
introduction therefore did not compel respondent to become a witness
against himself in violation of the Fifth Amendment.") (citing
Schmerber v. California, 384 U.S. 757, 761 (1966)).

[18] The possibility
of a testimonial key suggests one respect in which use immunity
may be broader than transactional immunity. Transactional immunity
extends "absolute immunity against future prosecution for
the offense to which the question relates." Counselman v.
Hitchcock, 142 U.S. 547, 586 (1892). Use immunity, by contrast,
requires the prosecution to show that "the evidence it proposes
to use is derived from a legitimate source wholly independent
of the compelled testimony." Kastigar v. United States, 406
U.S. 441, 460 (1972). "Immunity from the use of compelled
testimony, as well as evidence derived directly and indirectly
therefrom, affords this protection." Id. at 453.
Thus, transactional immunity for the compulsory production of
the cryptographic key would extend protection only to the offense
mentioned in the testimonial key, not to the wholly unrelated
transaction mentioned in the document. In the example in the text,
that might be fornication in Massachusetts or using Woodsy Owl
to advertise one's 4-H group. Because the plaintext of the document
is derived from the key, the protection under use immunity must
extend to the wholly unrelated crime mentioned in the document--say,
a bank robbery. Whether the Supreme Court in a future case that
raises this issue remains true to its verbal formulations is beyond
the scope of this paper.

[19] One difference
that may be significant as an evidentiary matter, but which will
not alter duties to produce the key, is that a cryptographic key
that encrypts documents may not be able to decrypt them. Froomkin,
supranote 2, at 890-94
(describing public-key encryption). By contrast, a safe-deposit
box key that locks the box must be capable of opening the box.
Public-key encryption means that one cannot assume that the possessor
or even the encrypter of encrypted files can decrypt them. Thus,
even if the government finds encrypted files in a person's possession,
a dishonest possessor may be credibly able to deny the ability
to decrypt the documents.

[20] Doe v. United
States, 487 U.S. 201, 210 n.9 (1988) (Doe II). The Court had earlier
suggested that the privilege could exist with respect to a combination
to a safe. Couch v. United States, 409 U.S. 322, 333 & n.16
(1973) (citing United States v. Guterma, 272 F.2d 344 (2d Cir.
1959)).

[26]Id. Cf.
Braswell v. United States, 487 U.S. 99, 126 (1988) (Kennedy, J.,
dissenting) ("Physical acts will constitute testimony if
they probe the state of mind, memory, perception, or cognition
of the witness").

[27] Although Counselman
v. Hitchcock, 142 U.S. 547, 586 (1892), held that a guarantee
of immunity, "to be valid, must afford absolute immunity
against future prosecution for the offense to which the questions
relates," Kastigar held that this "transactional
immunity" was unnecessary, so long as the prosecution showed
that "the evidence it proposes to use is derived from a legitimate
source wholly independent of the compelled testimony." Kastigar
v. United States, 406 U.S. 441, 460 (1972). "Immunity from
the use of compelled testimony, as well as evidence derived directly
and indirectly therefrom, affords this protection." Id.
at 453.

[34]Id. at
613. Moreover, as the Fisher Court observed, because the
papers belonged to the accountant, the taxpayers' production of
the papers would not serve to authenticate or vouch for the accuracy
of the accountant's work. Fisher, 425 U.S. at 413. See
also Braswell v. United States, 487 U.S. 99, 104 n.3 (1988).
AccordIn re Grand Jury Proceedings: Subpoenas for
Documents, 41 F.3d 377, 380 (8th Cir. 1994) (barring production,
because the government could not independently authenticate the
documents and failed to provide use immunity).

[36]Braswell,
487 U.S. at 130 (Kennedy, J., dissenting) (noting that once immunity
is granted, the government "would be free to use the contents
of the records against everyone, and it would be free to use any
testimonial act implicit in production against all but the custodian
it selects."). Cf. Doe I, 465 U.S. at 617 n.17 (1984)
(rejecting the argument that "any grant of use immunity must
cover the contents of the documents as well as the act of production",
because "use immunity need only protect . . . from the self-incrimination
that might accompany the act of producing. . . .").

[37]Fisher
also cannot and does not purport to represent a holding on the
subject of the production of papers written by the person under
subpoena. See Fisher, 425 U.S. at 394 (the items sought
were written by the accountant, with the possible exception of
some correspondence that would have been seizable under the Boyd
case as an instrumentality of fraud).

[45]Id. Kastigar,
by suggesting that one can use the coerced confession cases to
show when the use of evidence derived from compelled statements
is impermissible, shows that a causal relationship between the
compelled testimony and the evidence sought to be introduced is
enough. See id. at 461.

[46]Kastigar,
406 U.S. at 458-59 (quoting Murphy v. Waterfront Comm'n, 378 U.S.
52, 79 (1964)). Use immunity applies to "the compelled testimony
and its fruits." Murphy v. Waterfront Comm'n, 378 U.S. 52,
79 (1964). Under this rule, the prosecutors in a second proceeding
"have the burden of showing that their evidence is not tainted
by establishing that they had an independent, legitimate source
for the disputed evidence." Id. at 79 n.18.

[47] That the test
is one of cause in fact and not one of the use of the compelled
testimony itself seems clear from the Court's use of the "fruit
of the poisonous tree" analysis. See Kastigar, 406
U.S. at 461. However, the analysis is stricter for compelled testimony.
Id. If the motive for a witness' testimony is immunized
testimony, the testimony of the witness who was motivated by the
immunized testimony cannot be used. United States v. North, 920
F.2d 940, 942 & n.1 (D.C. Cir. 1990) (citing United States
v. Brimberry, 803 F.2d 908, 915-17 (7th Cir. 1986); United States
v. Hampton, 775 F.2d 1479, 1489 (11th Cir. 1985); United States
v. Kurzer, 534 F.2d 511, 517-18 (2d Cir. 1976)).

[50] Gouled v. United
States, 255 U.S. 298, 306 (1921) (Clarke, J., for a unanimous
court). Gouled expressly held that when a government agent
seized documents in violation of the Fourth Amendment, their introduction
into court violated the Fifth Amendment. Id. See also,
e.g., Olmstead v. United States, 277 U.S. 438, 478-79 (1928)
(Brandeis, J., dissenting) ("To protect that right [of privacy],
every unjustifiable intrusion by the Government upon the privacy
of the individual, whatever the means employed, must be deemed
a violation of the Fourth Amendment. And the use, as evidence
in a criminal proceeding, of facts ascertained by such intrusion
must be deemed a violation of the Fifth."); Silverthorne
Lumber Co. v. United States, 251 U.S. 385, 391 (1920) (Holmes,
J.).

[52] Braswell v.
United States, 487 U.S. 99, 130 (1988) (Kennedy, J., dissenting)
(once immunity is granted, the government "would be free
to use the contents of the records against everyone, and it would
be free to use any testimonial act implicit in production against
all but the custodian it selects").

[53] A possible analogy
is the compulsory interpretation of documents. My research has
turned up no cases involving interpretation. Independently, Froomkin
states, "I have been unable to find a single criminal case
in which the government has attempted to force a defendant to
translate her message." Froomkin, supranote
2, at 866n.687.
One civil case upheld a witness' refusal to explain a tape, though
he was the only one who could do it. Traficant v. Commissioner,
89 T.C. 501 (1987), aff'd, 884 F.2d 258 (6th Cir. 1989).
The compulsory production of a cryptographic key is not so invasive
in one respect as compulsory interpretation, because there is
no judgment involved or continuing cognitive work involved in
producing the key: either it works or it does not work.

[70] Hale v. Henkel,
201 U.S. 43, 74-75 (1906). Thus, where privacy is not an issue,
as under the Fourth Amendment's protection from searches and seizures
and the takings clauses, the corporations have the same rights
as individuals. Id. at 76.

[73]Id. at
634-35. Cases after Boyd observe that a search for papers
that the government seizes by main force was as much a "physical
compulsion" as the threat of a contempt sentence for failure
to produce. See, e.g., Gouled v. United States, 255 U.S.
298, 305-06 (1921).

[99]Couch,
409 U.S. at 328. This is congruent with the Fourth Amendment,
which does not protect misplaced confidence, and so avoids privacy
issues. Hoffa v. United States, 385 U.S. 293, 302 (1966).

[101]Id.
The Court rejected Justice Harlan's argument that "Saline
Bank stands for no constitutional principle whatever."
Murphy v. Waterfront Comm'n, 378 U.S. 52, 69 n.11 (1964) (criticizingHutcheson v. United States, 369 U.S. 599, 608 n.13 (1962)
(Harlan, J., plurality opinion) (citing 2 JOSEPH
STORY, COMMENTARIESON EQUITY, §
1494 n.1 (1836))).
Early commentators have likewise concluded that the privilege
protects against "the production of documents or chattels
by a person (whether ordinary witness or party witness) in response
to a subpoena, or to a motion to order production, or to other
form of process relying on his moral responsibility for truthtelling."
See 8 WIGMORE, supranote 21, § 2264, at 379 n.1 (emphasis in
original). Pennsylvania v. Muniz, 496 U.S. 582 (1990), goes beyond
Wigmore by prohibiting the use of information that was not sought
for its truth and by suggesting that prohibition extends to the
use of physical data as part of a lie-detector test. Wigmore does
suggest that the testimonial content is "the witness' assurance,
compelled as an incident of the process, that the articles produced
are the ones demanded." Id. at 380, cited with
approval in Fisher v. United States, 425 U.S. 391, 411 (1975).

[111]Id.
("Thus, although the Fifth Amendment may protect an individual
from complying with a subpoena for the production of his personal
records in his possession because the very act of production may
constitute a compulsory authentication of incriminating information,
. . . a seizure of the same materials by law enforcement officers
differs in a crucial respect, -- the individual against whom the
search is directed is not required to aid in the discovery, production,
or authentication of incriminating evidence."). Id.

[116] Johnson v.
United States, 228 U.S. 457, 458 (1913). Holmes' opinion was quoted
by the Court in Couch v. United States, 409 U.S. 322, 328 (1973).
Couch further suggested that the Fifth Amendment might
be violated by "[i]nquisitorial pressure . . . to . . . produce
incriminating documents," but there was no such pressure
"[i]n the present case." Id. at 329.

[127]Id.
at 411. (The Court's concern for testimonial incrimination may
have been dictated by Curcio v. United States, 354 U.S. 118, 125
(1957), which held that because production identified and authenticated
a document, further compulsory identification or authentication
did not violate the privilege.)

[129] The Court
has the power to fashion a common-law privilege under Federal
Rule of Evidence 501. Cf. Trammel v. United States, 445
U.S. 40 (1980) (narrowing common law privilege against adverse
spousal testimony). The Court has in the past held that a privilege
exists against discovery of material that would expose a party
to penalties. United States v. Saline Bank, 26 U.S. (1 Pet.) 100,
104 (1828) (Marshall, C.J.) ("The rule clearly is, that a
party is not bound to make any discovery which would expose him
to penalties, and this case falls within it."). Of course,
a non-constitutional privilege rule would not apply to the states
or, in current law, in diversity cases in federal court. FED. R. EVID. 501.

[142]See Warden,
387 U.S. at 310 (Fortas, J., joined by Warren, C.J., concurring
in the result) (rejecting the "totally unnecessary . . .
repudiation of the so-called 'mere evidence' rule").

[143]Id.
at 305-06 (citing Silverthorne Lumber Co. v. United States, 251
U.S. 385 (1920) (Holmes, J.); Gouled v. United States, 255 U.S.
298, 308-09 (1921)). Moreover, even if there were no protection
against the government's seizure of the property, a search might
still offend the Fourth Amendment. See United States v.
Jacobsen, 466 U.S. 109, 122 n.22 (1984).

[154] Harlow v.
Fitzgerald, 457 U.S. 800, 818 (1982) (providing immunity from
a civil claim "insofar as [defendants'] conduct [did] not
violate clearly established statutory or constitutional rights
of which a reasonable person would have known").

[155] California
v. Greenwood, 486 U.S. 35, 44 (1988) (using privacy, not property
arguments, to uphold a search and seizure of garbage, despite
the state court's decision that state law created property interests
in garbage). Some state courts have subsequently rejected the
United States Supreme Court's finding that there is no reasonable
expectation of privacy in garbage. State v. Hempele, 576 A.2d
793 (N.J. 1990); State v. Boland, 800 P.2d 1112 (Wash. 1990).

[158] Griswold
v. Connecticut, 381 U.S. 479, 509 (1965) (Black, J., dissenting)
("'Privacy' is a broad, abstract and ambiguous concept which
can easily be shrunken in meaning but which can also, on the other
hand, easily be interpreted as a constitutional ban against many
things other than searches and seizures.").